Hoists are a kind of typical rotating machinery widely applied in mines, and, as the “throats” of mines, take a very important role in the production in mines. As the modern industry and technology are developed rapidly and the requirement for high production efficiency is increasing, the structure of mine hoists becomes more and more complex, the hoisting capacity per run gets bigger and bigger, and the hoisting speed gets faster and faster, and hoisting distance gets longer and longer. Once a failure such as jamming, slipping, over-winding, or over-release occurs in the hoisting process of a mine hoist, a chain reaction may be triggered, and the hoisting condition not only affects the run of the equipment itself but also impacts subsequent production, and may even cause disastrous accidents and severe loss in national economy. Hence, it is necessary to monitor torque of the main shaft of mine hoists, because the torque of main shaft will change accordingly once jamming, slipping, over-winding, or rope breaking occurs on mine hoists.
Up to now, many torque measuring methods and devices have been invented. For example, a serials connection measurement method, in which a torque measuring device is connected in series on the tested unit, can be used. However, this method requires a change in the structural connection of the original tested unit and the cost will be high when it is applied to equipment that has been installed. Though the shaft torque can be measured by attaching strain foils to the shaft, the strain foils may fall off and the requirement for the precision of attachment of the strain foils is very high. Alternatively, though the shaft torque also can be measured by means of electromagnetic induction, electromagnetic induction may impact the effective transmission of wireless data. A shaft torque measuring method in which the shaft surface is treated appropriately (scribing lines, or installing coils, etc.) and then measuring devices are mounted at corresponding positions to realize the shaft torque measurement, requires one to mount supports on the original foundation and needs a large amount of connecting wires; hence, it is limited in application.